Gotland is more or less a large hunk of limestone in the middle of the Baltic Sea exposed to the wind and waves. There’s so much limestone that one of only two cement plants in all of Sweden is in the town of Slite on Gotland. The exposed limestone along the coast has been eroded over the millennia to create formations known as Raukar. Some are even part of reefs that were under water during the Silurian period.
The beaches on Gotland were quite stony and often contained significant amounts of (rotting) seaweed/slime. There were a few places that were decent for swimming though. Many of them have remnants of former fishing villages (fiskläge) that were often just a few basic communal buildings and a rudimentary boat launch. Since people tended to live up the cliffs and away from the water the fiskläge provided some basic shelter for the fishers before taking their catch home.
Here are some scenes from the beaches or nearby: